I did just that in addition to having a few browser windows open, and I'm not noticing any issues at all. CPU use is hovering around 10% and i can't even find a single stutter to complain about.

Now I'll admit that Haiku could probably do this on slower hardware than what I'm running, but I don't think a Q6600 CPU, 4GB RAM, and a Radeon 3870 GPU are that much more powerful than what the typical user runs today.

BeOS did that with a few MHz, <256MB of RAM and software rendering. I guess all that glossy stuff doesn't help if you need a powerful computer to do what was possible 10 years ago.